1. Field of the Invention
This invention relates to metallized multilayer films and, more particularly, to metallized films having a substrate which includes poly(vinylidine fluoride) and poly(methyl methacrylate).
2. Description of the Related Art
Metallized films, that is, films comprising a polymeric substrate on which has been deposited a layer of metal, are often employed in, for example, the automotive, furniture, stationery, interior building material, and advertising industries so as to provide an aesthetic or decorative enhancement to manufactured articles. Such films, in order to be commercially useful as decorative and aesthetic enhancements, should possess several characteristics.
For example, the substrate layer should be highly transparent so as not to detract from the reflective quality of the metal layer and the overall appearance of the article. The films should also exhibit good heat stability, especially when employed in the construction of outdoor signs, motor vehicles and other articles where high temperatures may be encountered. For example, the interior of a motor vehicle on a warm, sunny day in certain climates may experience temperatures in excess of 90.degree. C.
Flexibility is another desirable quality because flexible films are more readily applied to rough or uneven surfaces and multifaceted articles having a compound geometry. In still other applications, metallized multilayer films may be embellished with printed messages, decorative patterns, or complementary decorative transparent, colored layers. Metallized films, in order to be commercially useful, should readily accept printing and should be susceptible to the adhesion of further decorative layers thereto. Such films should also possess excellent adhesion between the metal and substrate layers. The films should be capable of being applied in an economical manner and retain a quality appearance without developing bubbles, wrinkles, swells or the like. Once applied, the films should remain durable and exhibit good resistance to a wide variety of weathering and environmental conditions.
Those metallized films which are presently known exhibit some, but not all, of these desirable features. Thus, while being useful in particular applications, the presently known films may not be broadly employed in a diverse myriad of circumstances. For example, metallized polyester films (as described in the Plastic Handbook published by Asakura Shoten), while being transparent and heat stable, have poor flexibility and exhibit, at best, only fair post-application durability. Various metallized polyester films are commercially available and have been for many years. Metallized acrylic films described in Plastic Material Course, Volume 12, Acrylic Resin, published by Nikkan Kogyo Shimbunsha, while being transparent and having good adhesion between the metal layer and the acrylic resin substrate, do not exhibit good heat stability or flexibility.
Metallized films comprising a metal layer deposited on a single layer fluoropolymer substrate have fair heat stability and durability, as well as good adhesion between the metal layer and the fluoropolymer substrate. However, these films are not readily printable. Films of this type are illustrated in Japanese Patent Kokai No. 22973/72, Japanese Patent Kokai No. 71249/85, and Japanese Utility Model Kokai No. 87027/88.
The performance characteristics of the presently known metallized films are summarized in Table I below.
TABLE I __________________________________________________________________________ PERFORMANCE CHARACTERISTIC METALLIZED Heat Flexi- Print- Metal Layer Durability FILM SUBSTRATE Transparency Stability bility ability Adhesion After Application __________________________________________________________________________ Polyester .largecircle. .largecircle. X .DELTA. .largecircle. .DELTA.-X Acrylic .largecircle. X X .DELTA. .largecircle. .DELTA.-X Fluoropolymer .DELTA.-X .largecircle.-.DELTA. .DELTA. X .largecircle. .DELTA. (single layer) __________________________________________________________________________ .largecircle.: Good .DELTA.: Fair X: Poor
A double layer film believed to include a first layer having 80% poly(vinylidine fluoride) and 20% poly(methyl methacrylate) and a second layer having 20% poly(vinylidine fluoride) and 80% poly(methyl methacrylate) is commercially available in Japan from Denki Kagaku Kogyo K.K. as DENKA DX-Film. The film is stated to exhibit excellent weatherability and may be used as a protective cover for metal and plastic boards, as a protective cover for tent clothes, and as a protective or a decorative cover for various substrates. The DENKA DX-Film does not include a metal layer.
Accordingly, there remains a need for a metallized film which is transparent, heat stable, flexible, readily printable, durable after being applied, and wherein the metal layer has good adhesion to the film substrate.